首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3910篇
  免费   280篇
  国内免费   32篇
耳鼻咽喉   56篇
儿科学   210篇
妇产科学   44篇
基础医学   506篇
口腔科学   235篇
临床医学   300篇
内科学   793篇
皮肤病学   159篇
神经病学   225篇
特种医学   166篇
外科学   634篇
综合类   38篇
现状与发展   1篇
预防医学   332篇
眼科学   79篇
药学   140篇
肿瘤学   304篇
  2021年   42篇
  2020年   34篇
  2019年   38篇
  2018年   43篇
  2017年   42篇
  2016年   35篇
  2015年   41篇
  2014年   63篇
  2013年   88篇
  2012年   128篇
  2011年   163篇
  2010年   102篇
  2009年   104篇
  2008年   152篇
  2007年   190篇
  2006年   172篇
  2005年   170篇
  2004年   178篇
  2003年   159篇
  2002年   148篇
  2001年   174篇
  2000年   131篇
  1999年   123篇
  1998年   60篇
  1997年   67篇
  1996年   43篇
  1995年   48篇
  1994年   32篇
  1993年   34篇
  1992年   90篇
  1991年   100篇
  1990年   83篇
  1989年   91篇
  1988年   96篇
  1987年   74篇
  1986年   86篇
  1985年   89篇
  1984年   71篇
  1983年   68篇
  1982年   31篇
  1981年   30篇
  1980年   31篇
  1979年   46篇
  1977年   33篇
  1976年   32篇
  1975年   36篇
  1974年   29篇
  1973年   40篇
  1971年   28篇
  1970年   33篇
排序方式: 共有4222条查询结果,搜索用时 15 毫秒
31.
BACKGROUND: Boys and young men with hemophilia treated with factor infusions before 1985 had a substantial risk of acquiring the human immunodeficiency virus (HIV) and the acquired immunodeficiency syndrome. This study was designed to assess the effects of HIV and hemophilia per se on neurological function in a large cohort of subjects with hemophilia, and to investigate the relationships between neurological disease and death during follow-up. METHODS: Three hundred thirty-three boys and young men (207 HIV seropositive and 126 HIV seronegative) were evaluated longitudinally in a multicenter, multidisciplinary study. Neurological history and examination were conducted at baseline and annually for 4 years. The relationship between neurological variables, HIV serostatus, CD4+ cell counts, and vital status at the conclusion of the study was examined using logistic regression models. RESULTS: The risks of nonhemophilia-associated muscle atrophy, behavior change, and gait disturbance increased with time in immune compromised HIV-seropositive subjects compared with HIV seronegative or immunologically stable HIV-seropositive subjects. The risk of behavior change in immune compromised HIV-seropositive hemophiliacs, for example, rose to 60% by year 4 versus 10% to 17% for the other study groups. Forty-five subjects (13.5%), all of whom were HIV seropositive, died by year 4. Subjects who died had had increased risks of hyperreflexia, nonhemophilia-associated muscle atrophy, and behavior change. CONCLUSIONS: These results indicate that immune compromised, HIV-seropositive hemophiliacs have high rates of neurological abnormalities over time and that neurological abnormalities were common among subjects who later died. By contrast, immunologically stable HIV-seropositive subjects did not differ from the HIV-seronegative participants. Hemophilia per se was associated with progressive abnormalities of gait, coordination, and motor function.  相似文献   
32.
Purpose: To determine the impact of whole pelvic irradiation on the risk of PSA failure in prostate cancer patients, at high predicted risk for lymph node involvement, receiving definitive radiotherapy.

Materials and Methods: Between October 1987 and December 1995, 506 patients with clinically localized prostate cancer were treated with definitive radiotherapy at UCSF and affiliated institutions. Treatment consisted of 4-field whole pelvic irradiation followed by a prostate-only boost, or prostate-only treatment (median follow-up was 35 months and 30 months, respectively). PSA failure was defined as: 1. a PSA value ≥ 1 ng/ml; or 2. a PSA value that rose ≥ 0.5 ng/ml in ≤ 1 year posttreatment on two consecutive measurements, with the first rise defined as the time of failure. The calculated risk of lymph node positivity (%rLN+) was defined as (iPSA) + 10(GS-6), and high risk was defined as %rLN+ ≥ 15%. Univariate and multivariate analyses were performed.

Results: A total of 201 high-risk patients were identified. High-risk patients who received whole pelvic irradiation had significantly improved freedom from PSA failure compared to those who received prostate-only treatment (median PFS = 34.3 months vs. 21.0 months; p = 0.0001). Potential confounding variables, including initial PSA, Gleason score, T stage, radiation dose, year of treatment, use of three-dimensional (3D) conformal techniques, and use of hormone therapy, did not account for the observed difference in time to PSA failure. Multivariate analysis revealed type of radiation treatment to be the most significant independent predictor of outcome.

Conclusion: Whole pelvic radiotherapy significantly improves the PSA failure-free survival in patients with a high calculated risk of lymph node positivity.  相似文献   

33.
34.
35.
Rheumatoid arthritis (RA) and osteoarthritis (OA) are prevalent chronic health conditions. However, despite recent advances in medical therapeutics, their treatment still represents an unmet medical need because of safety and efficacy concerns with currently prescribed drugs. Accordingly, there is an urgent need to develop and test new drugs for RA and OA that selectively target inflamed joints thereby mitigating damage to healthy tissues.Conceivably, biocompatible, biodegradable, disease-modifying antirheumatic nanomedicines (DMARNs) could represent a promising therapeutic approach for RA and OA. To this end, the unique physicochemical properties of drug-loaded nanocarriers coupled with pathophysiological characteristics of inflamed joints amplify bioavailability and bioactivity of DMARNs and promote their selective targeting to inflamed joints. This, in turn, minimizes the amount of drug required to control articular inflammation and circumvents collateral damage to healthy tissues. Thus, nanomedicine could provide selective control both in space and time of the inflammatory process in affected joints.However, bringing safe and efficacious DMARNs for RA and OA to the marketplace is challenging because regulatory agencies have no official definition of nanotechnology, and rules and definitions for nanomedicines are still being developed. Although existing toxicology tests may be adequate for most DMARNs, as new toxicity risks and adverse health effects derived from novel nanomaterials with intended use in humans are identified, additional toxicology tests would be required. Hence, we propose that detailed pre-clinical in vivo safety assessment of promising DMARNs leads for RA and OA, including risks to the general population, must be conducted before clinical trials begin.  相似文献   
36.
37.
Constitutional pure red cell aplasia (CPRCA) is a syndrome of failed erythropoiesis usually diagnosed within the first year of life. Four patients with CPRCA received transplants with marrow from their HLA- identical, mixed lymphocyte culture-nonreactive siblings. All patients were resistant to corticosteroid therapy and were dependent on regular red cell transfusions for at least 5 years. Three patients were conditioned with procarbazine, antithymocyte globulin, cyclophosphamide, and busulfan, and one was conditioned with antithymocyte serum, cyclophosphamide, and busulfan. Three patients promptly had successful engraftments with establishment of donor hematopoiesis. One patient initially rejected his graft but received a successful retransplant. All patients are currently alive with Karnofsky performance scores of 100 and normal erythropoiesis of donor origin. Despite a history of multiple transfusions, bone marrow transplantation is a potentially curative therapy for patients with CPRCA.  相似文献   
38.
Background: Children and parents experience significant anxiety and distress during the preoperative period. Currently available interventions are having limited efficacy. Based on an integration of the literature in both the anesthesia and psychological milieus, the authors developed a behaviorally oriented perioperative preparation program for children undergoing surgery that targets the family as a whole.

Methods: Children and their parents (n = 408) were randomly assigned to one of four groups: (1) control: received standard of care; (2) parental presence: received standard parental presence during induction of anesthesia; (3) ADVANCE: received family-centered behavioral preparation; and (4) oral midazolam. The authors assessed the effect of group assignment on preoperative anxiety levels and postoperative outcomes such as analgesic consumption and emergence delirium.

Results: Parents and children in the ADVANCE group exhibited significantly lower anxiety in the holding area as compared with all three other groups (34.4 +/- 16 vs. 39.7 +/- 15; P = 0.007) and were less anxious during induction of anesthesia as compared with the control and parental presence groups (44.9 +/- 22 vs. 51.6 +/- 25 and 53.6 +/- 25, respectively; P = 0.006). Anxiety and compliance during induction of anesthesia was similar for children in both the ADVANCE and midazolam groups (44.9 +/- 22 vs. 42.9 +/- 24; P = 0.904). Children in the ADVANCE group exhibited a lower incidence of emergence delirium after surgery (P = 0.038), required significantly less analgesia in the recovery room (P = 0.016), and were discharged from the recovery room earlier (P = 0.04) as compared with children in the three other groups.  相似文献   

39.
Fifteen skeletally immature patients with double major adolescent idiopathic scoliosis with large lumbar curves and notable L4 and L5 coronal plane obliquity were retrospectively studied. Seven patients who underwent anterior release and fusion of the lumbar curve with segmental anterior instrumentation and subsequent posterior instrumentation ending at L3 were compared with eight patients treated with anterior release and fusion without anterior instrumentation followed by posterior instrumentation to L3 or L4. At 4.5 years follow-up (range 2.5-7 years), curve correction, coronal balance and fusion rate were not statistically different between the two groups; however, the group with anterior instrumentation had improved coronal plane, near normalangulation in the distal unfused segment compared with the group without anterior instrumentation. In cases involving severe lumbar curvatures in the context of double major scoliosis, when as a first stage anterior release is chosen, the addition of instrumentation appears to restore normal coronal alignment of the distal unfused lumbar segment, and may in certain cases save a level compared with traditional fusions to L4.  相似文献   
40.

Background

The clinical trials mechanism of standardized treatment and follow-up for cancer patients with similar stages and patterns of disease is the most powerful approach available for evaluating the efficacy of novel therapies, and clinical trial participation should protect against delivery of care variations associated with racial/ethnic identity and/or socioeconomic status. Unfortunately, disparities in clinical trial accrual persist, with African Americans (AA) and Hispanic/Latino Americans (HA) underrepresented in most studies.

Study Design

We evaluated the accrual patterns for 10 clinical trials conducted by the American College of Surgeons Oncology Group (ACOSOG) 1999–2009, and analyzed results by race/ethnicity as well as by study design.

Results

Eight of 10 protocols were successful in recruiting AA and/or HA participants; three of four randomized trials were successful. Features that were present among all of the successfully recruiting protocols were: (1) studies designed to recruit patients with regional or advanced-stage disease (2 of 2 protocols); and (2) studies that involved some investigational systemic therapy (3 of 3 protocols).

Discussion

AA and HA cancer patients can be successfully accrued onto randomized clinical trials, but study design affects recruitment patterns. Increased socioeconomic disadvantages observed within minority-ethnicity communities results in barriers to screening and more advanced cancer stage distribution. Improving cancer early detection is critical in the effort to eliminate outcome disparities but existing differences in disease burden results in diminished eligibility for early-stage cancer clinical trials among minority-ethnicity patients.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号